WO2008080385A1

WO2008080385A1 - Method and device for sensing the three-dimensional surface of an object, in particular of a vehicle tire

Info

Publication number: WO2008080385A1
Application number: PCT/DE2007/002282
Authority: WO
Inventors: Wolfgang Pogade
Original assignee: Chronos Vision Gmbh
Priority date: 2006-12-28
Filing date: 2007-12-18
Publication date: 2008-07-10
Also published as: DE102006062447B4; DK2106530T3; EP2106530B1; DE102006062447A1; EP2106530A1; ES2403030T3

Abstract

In a method for sensing the three-dimensional surface of an object, a vehicle tire, for example, a light beam (12a) is emitted by a light source (11) and projected at an angle onto the surface (16a) of the object (16) to be sensed. The light beam (12b) reflected by the surface (16a) is sensed by an optical sensor (15), and the surface (16a) of the object (16) is determined from the image data. The light beam (12a) projected onto the surface (16a) of the object (16) is displaced by means of a rotating prism (13) parallel to the beam axis of said light beam (12a) in such a way that said light beam (12a) passes over the surface (16a) of the object (16) to be sensed under a constant angle of incidence (α). Tire profiles of motor vehicle tires in particular are measured. The measurement device (10) has a laser (11), a rotatable prism (12), and a mirror device (14).

Description

Method and device for detecting the three-dimensional surface of an object, in particular a vehicle tire

The present invention relates to a method for detecting the three-dimensional surface of an object according to the preamble of patent claim 1, and to a device for detecting the three-dimensional surface of an object according to the preamble of patent claim 10.

Capturing object surfaces is important in various applications. For example, in traffic engineering there is a need to control the condition of tire surfaces and to measure the tread depth of motor vehicle tires. In traffic monitoring or traffic engineering, traffic safety can be considerably increased by rapid measurement of the tread depths of motor vehicle tires. It is desirable if the measurement can be made for example on the moving vehicle. By measuring the tread depth of motor vehicle tires in flowing traffic, it would be possible to identify vehicles with insufficient tire tread, which could better enforce compliance with legal requirements.

But also in the industrial manufacturing of products, the registration of the surface is important, for example to perform quality controls, or to manufacture products in automated processes.

In the prior art, three-dimensional surfaces are detected or measured, for example, by means of the light-section triangulation method. In this case, a surface is obliquely illuminated with a light beam or a lighting line and the light beam reflected back from the object surface is detected. From the displacement of the reflected beam of light, which is dependent on the position of the _j eweiligen reflection point on the object surface, the surface structure is determined. The document DE19705047A1 shows, for example, a method and a device for measuring the tread depth of a motor vehicle tire, in which the tire tread is exposed to laser light and the light reflected from the tire tread is detected by an image-resolving sensor. The image-resolving sensor observes the shape of the light spot and generates output data in accordance with the profile depth. During the measurement, the motor vehicle tire is rotated in order to be able to carry out the measurement at several points of the tire profile. The measurement is performed, for example, on a brake tester in which the tire rotates while being exposed to the laser light.

The documents WO96 / 37754 and DE4316984A1 respectively show methods and devices for determining the tread depth of vehicle tires in which the light-section triangulation method is performed, wherein the measuring device is moved relative to the object or tire surface to detect the surface.

Methods for tire profile measurement in flowing traffic are disclosed, for example, in the publications DE-OS1809459 and EP0469948A1. In this case, for example, stationary measuring devices are used out of a pit, which project a single measuring line onto the object in order to obtain an evaluatable profile line therefrom. In order to obtain increased evaluation reliability, several such systems are provided one behind the other.

The document DE10141363A1 generally describes a scanning device wherein a scanning beam is projected onto a scene to be examined by a rotating transmitted-light prism. However, the method and the arrangement shown there are not suitable for triangulation, since the scanning beam and the reflection beam lie in one plane.

It is the object of the present invention to provide a method and a device, with which a resting object surface by means of the light-cut - triangulation in a very short time and at high speed can be measured automatically. In particular, the tread depth of motor vehicle tires in flowing traffic should be measured.

This object is achieved by the method for detecting the three-dimensional surface of an object according to claim 1, as well as by the device for detecting the three-dimensional surface of an object according to claim 10. Further advantageous features and details of the invention will become apparent from the dependent claims, the description and the drawings.

In the method for detecting the three-dimensional surface of an object according to the invention, a light beam is emitted from a light source and projected obliquely onto a surface of the object to be detected, and the light beam reflected from the surface is detected by an optical sensor to extract image data from the optical Sensor are generated to determine the surface of the object, wherein the projected onto the surface of the object light beam is moved by means of a rotating prism in parallel to its beam axis, so that it covers the surface of the object to be detected at a constant angle of inclination α.

By means of the method according to the invention, the light beam can be guided over the object surface at a particularly high speed, so that the area of the surface detected by the light beam can be measured with the light-section triangulation method. In particular, with the method a partial area of the surface of a motor vehicle tire can be detected in such a short time that the measurement of the tread depth in flowing traffic is possible.

Advantageously, the light beam is shaped as a two-dimensional illumination line which extends transversely to the beam axis, wherein the illumination line projected onto the surface to be detected is displaced in parallel during the measurement. As a result, an entire area of the surface can be detected, which is swept by the parallel moving illumination line. -A -

In particular, a vehicle tire is used as the object, for example, wherein the profile depth of the vehicle tire is determined from the image data.

Advantageously, the object is illuminated through a slit, the illumination line extending in the longitudinal direction of the slit and sweeping the width of the slit during the measurement. This is particularly advantageous in the case of tire tread depth measurement, for example when the gap is arranged in the roadway surface. For a short time, the tire to be measured presents itself to the light beam as it rolls over the gap. During the rolling process, the tire surface located on the gap is at rest relative to the measuring device. During this time, the tire surface resting on the gap can be detected with the method according to the invention and its tread depth can be measured.

Advantageously, the emitted light beam is directed after passing through the rotating primate by means of an adjustable mirror device on the object. As a result, the parallel moving light beam is directed in the direction of the object surface, wherein the beam direction in space, that is, the parallel displacement of the light beam is maintained.

Preferably, the emitted light beam passes through the rotating prism, being displaced in parallel, and then the light beam reflected from the object passes through the rotating prism a second time to cancel the parallel displacement caused by the first pass after reflection on the object. In other words, the reflection beam resulting from the measurement object, for example the motor vehicle tire, traverses the rotating prism a second time on the way to the optical sensor, but through a surface pair other than the emitted or primary light beam. This resulting reflection beam is therefore displaced in parallel during the second passage through the prism so that the parallel displacement that occurs during the first pass is canceled out again. As a result, the reflection beam moves, For example, which is present as a profile line, not relative to the optical sensor, although the illumination line or the primary light beam is displaced parallel during the rotation of the prism, for example, while sweeping the entire width of the observation slit.

Advantageously, the light beam transmitted to the object is aligned by means of the mirror device in such a way that it runs parallel to the light beam reflected by the object. Due to the fact that the light beam transmitted to the object and the light beam reflected by the object run parallel to each other in wide ranges, the dimensions of the measuring device can be kept particularly low. Furthermore, the mutual distance of the two parallel light beams can be adjusted or changed according to the desired application, so that the scope of the scanning is extremely flexible.

Preferably, the light beam is deflected before hitting the object by means of auxiliary mirrors so that it obliquely incident on the surface of the object.

According to another aspect of the invention, there is provided an apparatus for detecting the three-dimensional surface of an object comprising an optical sensor, a light source emitting a light beam, an optical device for projecting the emitted light beam inclined to a surface of the object to be detected. which detects the light beam reflected from the surface and generates image data, and an evaluation unit which determines from the image data of the optical sensor, the surface of the object, wherein a rotatable prism is provided which shifts the light beam projected onto the surface parallel to its beam axis, so he sweeps over the surface of the object to be detected at a constant inclination angle α.

The advantages of the device according to the invention are described by means of the method according to the invention. Advantageously, the light source is designed such that the light beam is formed as a line of illumination extending transversely to the beam direction, wherein the axis of rotation of the prism lies in the plane of the illumination line. As a result, the illumination line is moved parallel as it passes through the rotating prism, so that a portion of the surface is swept by the parallel moving illumination line.

Advantageously, the object is a vehicle tire, and the evaluation device is designed to determine the tread depth of the vehicle tire from the image data.

In particular, the rotatable prism has, for example, an even number of surfaces. The rotatable prism has in each case opposite, parallel aligned prism surfaces through which the emitted light beam is guided.

Preferably, the device comprises a wall in which a gap is formed, through which the object is illuminated, wherein the gap extends parallel to the illumination line, that is, in the longitudinal direction thereof. For example, the wall may be integrated into a roadway surface so that the tires of vehicles moving on the roadway roll on the nip and thus briefly present themselves to the light beam or line of illumination. During this time, the illumination line can be moved parallel across the gap width, so that the entire surface area of the object or vehicle tire, which rests on the gap, can be measured.

In particular, the dimensions of the prism can be selected such that the parallel displacement of the illumination line projected onto the surface to be detected essentially corresponds to the width of the gap.

Preferably, the optical device has at least one mirror pair with mutually inclined mirrors in order to direct the light beam onto the object, while being moved in parallel. As a result, the parallel displacement caused by the rotating prism is maintained even after reflection on the pair of mirrors.

Preference is given to _: the pair of mirrors displaceable in the beam direction and the angle between the two mirrors is adjustable, for example. As a result, the mirror pair can be precisely adjusted in order to align the light or measuring beam exactly on the measuring surface.

Advantageously, the rotatable prism is arranged in the beam path such that both the emitted light beam and the light beam reflected by the object pass through the same prism, so that the two parallel displacements of the light beam cancel each other when passing through the prism. As a result, the light beam reflected by the object or the profile line reflected by the object always strikes the optical sensor at the same point, which is, for example, a camera or part of a camera. That is, the resulting due to the parallel displacement on the object surface temporal change of the profile line is detected by the optical sensor and can then be evaluated.

Advantageously, the optical device is designed such that the light beam transmitted to the object runs substantially parallel to the light beam reflected by the object.

In particular, the optical device may comprise auxiliary mirrors which are arranged adjacent to the object and deflect the light beam directed onto the object in such a way that it obliquely strikes the surface of the object. As a result, the light-section triangulation method can also be carried out with an essentially parallel beam path. -o -

The device preferably comprises a housing which has windows with self-cleaning surfaces, through which the emitted and / or the light beam reflected by the object is guided.

The invention will now be described by way of example with reference to drawings, in which:

Fig. 1 shows a first preferred embodiment of the device according to the invention in a sectional view in principle;

Fig. 2 shows a perspective view of the device according to the invention during the measurement of the profile of a vehicle tire as an object;

Fig. 3a-d show the timing of the measurement of a tire profile schematically;

Fig. 4 shows a device according to a second preferred embodiment of the invention in a schematic sectional view, wherein the beam path is designed parallel;

Figures 5a and 5b illustrate the light-section triangulation method using the example of measuring a smooth surface;

Figures 6a and 6b illustrate the light-section triangulation method using the example of an uneven surface; and

Fig. 7 shows an example of a measurement image that was created with the device according to the invention and the method according to the invention. Advantages and features which are described in connection with the device according to the invention also apply to the method according to the invention and vice versa.

FIG. 1 shows a measuring device 10, which represents a first preferred embodiment of the invention and is designed to detect the three-dimensional surface of an object. The measuring device 10 has a light source 11 in the form of a laser, which emits a light beam 12a, as well as a rotatable prism 13 and a mirror device 14, which are successively arranged in the beam path. Furthermore, the measuring device 10 comprises an optical sensor 15, which is configured for example as a camera and detects the light beam 12b reflected by an object 16 to be measured. Furthermore, an evaluation unit 17 is provided which receives image data generated by the optical sensor 15 and determines the course of the surface of the object 16 from the image data.

In the present example, the laser 11 is designed so that it emits a light line 12a as an illumination line which extends transversely to the beam direction, that is, in the figure 1 perpendicular to the plane of the drawing. The rotatable prism 13 has an axis of rotation 18 which is directed perpendicular to the beam direction, so that the light beam 12a coming from the laser impinges successively on the different surfaces 13a, 13b, 13c, etc. of the prism 13 and passes through the prism 13. On a surface 13e opposite to the surface 13a through which the light beam 12a enters, the light beam 12a leaves the primate. In this case, the pairs of surfaces through which the light beam 12a enters and exits are each directed parallel to one another, so that the light beam 12a is continuously displaced in a direction parallel to the rotation axis of the prism 13 about the axis of rotation 18. The parallel displacement is caused by the optical effect of the plane-parallel plate, which is formed in the present case by the respective opposite parallel prism surfaces 13a, 13e. As soon as due to the rotation of the prism 13, the entry and exit of the light beam 12a by the next pair of prism surfaces, the light beam exiting the prism 13 returns to its original position and begins a new parallel shift. The mirror device 14 is arranged in the beam path behind the prism 13 and consists of a first surface mirror 14a and a second surface mirror 14b. The surface mirrors 14a, 14b are inclined relative to each other, so that the light beam 12a successively impinges on the two mirror surfaces and is directed in the direction of the object 16. The two mirrors 14a, 14b are connected to each other by a connecting hinge 19. By means of the connecting hinge 19, the second mirror 14b can be tilted in a tilting direction K relative to the first mirror 14a.

The entire mirror device 14 is displaceable in a direction L ₁ which is equal to the direction of the beam axis of the light beam 12 a. The tilting K of the mirror 14b and the displacement L of the entire mirror device 14 are effected by drive units not shown in the figure.

By means of the mirror device 14 and the rotating prism 13, which has an even number of prism surfaces, the light beam 12a is displaced parallel to the beam axis, while striking the surface 16a of the object 16. As a result, the angle of inclination α at which the light beam 12a impinges on the object surface remains constant, while the light beam 12a, which displaces in parallel, sweeps over the object surface.

The mirror device 14 and the prism 13 are arranged such that the light beam 12b reflected by the object 16 also passes through the prism 13, in turn entering and exiting through a pair of opposing prism surfaces. In the present case, the light beam 12a emitted by the laser 11 and the light beam 12b reflected by the object 16 pass through the prism 13 perpendicularly to one another, that is, the axis of rotation 18 of the prism and the two light beams 12a and 12b passing through the prism 13 are oriented orthogonal to one another. - -

Due to the geometric configuration of the prism 13 and the mirror device 14 with the resulting beam path, the light beam 12b emerging from the prism 13 always remains at the same position and with the beam direction unchanged. That is, the parallel shift of the light beam 12 a in the first pass through the prism 13 is canceled by the parallel displacement of the light beam 12 b in the second pass through the prism 13. Thus, the camera or optical sensor 15 and the entire measuring device 10 with the rotating prism 13 relative to the surface 16a of the object 16 remain at rest, while the surface 16a is swept by the light beam 12a or the illumination line.

Figure 2 shows the measuring device 10 in a perspective schematic representation in the measurement of a tire profile. Elements and components of the measuring device 10 which have already been described with reference to FIG. 1 are identified by the same reference numerals as in FIG.

The measuring device 10 shown in Figure 2 additionally comprises a housing 21 in which the parts of the measuring device, as already described in Figure 1, are arranged. The housing 21 has a protective function. In this case, the prism 13 is driven by a prism motor 22, which causes the rotation of the prism 13 about the axis of rotation 18. The prism 13 is surrounded by a reflex protection device 28. On the mirror device 14, a tilting mechanism 23 is arranged, which tilts the mirror 14b for the purpose of adjustment. In the present case, the tilting device 23 is configured as a rotary spindle in order to set the angle between the first mirror 14a and the second mirror 14b exactly.

In the housing 21, an exit window 24 is arranged, through which the light beam 12a emitted to the object 16 leaves the interior of the housing 21, and an entrance window 25 through which the light beam 12b reflected by the object 16 again enters the interior of the housing 21 a second time through the prism 13 and then to hit the camera or the optical sensor 15. The windows 24 and 25 of the housing 21 have surfaces, which have the well-known lotus effect for self-cleaning, so that the windows 24, 25 can be automatically cleaned when contaminated with a water spray.

In the example shown here, the object 16 is a vehicle tire whose tread depth is determined by means of the measuring device 10 in the form of a 3-D tire scanner. In the method and arrangement shown here, the light beam 12a that is sent to the object 16 and the light beam 12b reflected by the object 16 are in their full length on their way from the mirror 12b to the object 16 and from the object 16 to the rotatable prism 13, respectively inclined against each other.

Also in the example shown here, the light beam 12a is formed as a line of illumination which extends transversely to the beam direction and is projected onto the object 16 as a light line.

In this case, the light line is imaged through a gap 26, which is arranged in a wall 27, on the object 16, which here is a vehicle tire. In this case, the longitudinal direction of the gap 26 extends along the line of illumination formed by the light beam 12a. The width of the observation gap 26 is dimensioned such that the light beam 12a or the illumination line strikes the surface of the tire 16 during the entire parallel displacement. That is, the illumination line is adjusted so that it is parallel to the observation gap and fills the length thereof. The dimensions of the prism 13 are selected so that the displacement of the illumination line by rotation of the prism 13 covers exactly the width of the gap 26.

The arrangement of the surfaces of the prism 13 ensures that a change of the scanning plane takes place when due to the rotation of the prism 13 results in a change in the beam path of the illumination line side surface or prism surface. - -

Due to the inclination of the illumination line or the light beam 12a against the imaginary vertical of the object surface, the illumination line is changed by the surface structure of the reflection on the surface of the object 16 into a profile line which forms the reflected light beam 12b. As a result, the profile depth of the tire can be determined by means of triangulation and the surface structure can be measured. The imaginary vertical of the observation surface is shown in Figure 2 by the arrow U.

FIGS. 3a to 3b show a tire profile measurement as a special embodiment of the method according to the invention for detecting object surfaces. In each case, the measuring device is shown schematically with the laser 11, the rotating prism 13, the mirror device 14 and the camera 15 as an optical sensor. As an object 16, a vehicle tire rolls on a road surface 31, in which the observation gap 26 is arranged. While the tire 16 rolls over the gap 26, as shown in different phases in FIGS. 3a, 3b, 3c and 3d, an area of the vehicle tire 16 presents itself as a resting surface above the observation gap 26. The direction of travel is indicated by the arrow F and the rotation of the rolling tire represented by the arrow R.

While the tire surface rests over the nip 26 as it rolls over, the prism 13 rotates about its axis of rotation 18 and assumes the various positions shown in Figures 3a-3d.

At the beginning of the measurement (FIG. 3 a), the measuring light beam 12 a is offset parallel after passing through the prism 13 so that it hits the tire surface at the right edge of the gap 26 and is reflected therefrom. The illumination line on the tire surface, which extends in the figure perpendicular to the drawing surface, forms a profile line after the reflection. The reflected light beam 12b, which forms the profile line, in turn passes through the prism 13 and is also offset in parallel before it hits the camera 15. In the second phase of the rolling process (FIG. 3 b), the light beam emitted by the laser 11 passes vertically through the prism surfaces, so that no parallel offset takes place. After being deflected by the mirror device 14, the light beam 12a strikes the surface of the tire 16 as a line of illumination through the gap 26. From there it is reflected as a profile line in the direction of the prism 13, the reflected light beam 12b perpendicular to the emitted light beam 12a, the prism 13 goes through. In this case, due to the parallel priming surface when passing through the prism 13 also no parallel offset of the light beam 12b takes place. The reflected light beam 12b, which is a profile line, reaches the camera 15 which detects the profile line.

In the next two phases of the measuring process, shown in FIGS. 3c and 3d, the prism 13 continues to rotate, so that the light beam 12a shaped as a line of illumination shifts further parallel in the widthwise direction of the gap 26 until it reaches the left edge reaches the gap 26 (Figure 3d). By passing through the prism 13 twice, the reflected light beam 12b always remains in a constant position at the location of the optical sensor 15, while the light beam 12a transmitted to the object passes over the object surface. After the light beam has been translated in parallel across the nip width and has captured the presenting area of the tire surface, the tire surface disengages from the nip 26 by further rolling.

FIG. 4 schematically shows a further preferred embodiment of the invention, in which the light beam 12a guided to the object surface and the light beam 12b reflected by the object surface run for the most part parallel to one another. For this purpose, the measuring device 40 shown in FIG. 4 has a pair of auxiliary mirrors 41, 42, which are arranged relatively close to the object 16 to be detected. Elements and components of the measuring device 40, which are essentially functionally identical or identical to those of the measuring device 10, are identified in FIG. 4 by the same reference numerals as in FIGS. 1-3 and have already been described there. In the case of the measuring device 40, the rotatable prism 13 or rotary prism and the mirror device 14 are arranged in the beam path such that the light beam 12b reflected by the object extends parallel to this in a region P of the transmitted light beam 12a. In this case, the two light beams 12a and 12b pass through the prism 13 at an angle to each other, which is equal to the angle formed by the respective prism surfaces to each other, through which the two light beams 12a and 12b extend.

The two auxiliary mirrors 41 and 42 deflect the light beam 12a, which runs in the region P parallel to the reflected light beam 12b, before hitting the surface of the object 16 in such a way that the light beam 12a obliquely or obliquely impinges on the surface and thus the prerequisites to perform the light - cut triangulation method.

As a result, the distance between the measuring unit 40 and the object 16 can vary within a very wide range. An adjustment of the light beam 12a transmitted to the object 16, which represents the scanning beam, no longer necessarily has to be done by the adjustment of the mirror 14b of the mirror device 14. The mirrors 14a and 14b of the mirror device 14 are adjusted in this embodiment so that the beam 12a extends in the region P parallel to the reflected beam 12b at a distance Z to the latter. With the two auxiliary mirrors 41 and 42, the correct scanning angle is ensured when hitting the object 16. The auxiliary mirrors 41, 42 are accommodated in a separate device part Y of the measuring device 40. The remaining parts of the measuring device 40 are housed in the device part X, which is spatially separated from the device part Y. Due to the parallel beam path, the two device parts X and Y can have a variable within wide limits distance from each other, which can be significantly expand the scope of this scanner.

To illustrate the light-slit triangulation method used in the present invention, FIGS. 5a and 5b serve first. The light - section triangulation method is that of a Light source A1 projected onto an object to be examined E1 measuring line C1 from the lens of a camera B1 on the sensor surface of the camera B1. If the surface of the object E1 is flat, the measurement line C1 appears as a line D1 on the optical sensor of the camera B1. In order to obtain the structure of the entire surface, the measurement object E1 is displaced along a movement line F1, so that the measurement line C1 sweeps over the surface of the object E1 during the measurement process. During the measuring process, the sensor of the camera B1 records the image of the measuring line at short intervals and stores it. By comparing the measurement images, the surface of the measurement object, that is to say of the object E1 to be detected, can be calculated.

FIGS. 6a and 6b now show by way of illustration the measurement of the structured surface of an object E2 to be measured. In this case, the measuring line C2 projected by the light source A2 onto the object E2 is imaged by the lens of the camera B2 onto the sensor surface of the camera B2. In the case shown here, the surface of the object E2 is not flat, so that the measurement line C2 appears as a profile line D2 on the sensor of the camera B2. In order to obtain the structure of the total surface of the object E2, the object E2 is displaced along the movement line F2, so that the measurement line C2 as illumination line sweeps over the entire surface of the object E2 during the measurement process. During the measuring process, the sensor of the camera B2 records the image of the measuring line or profile line D2 at short intervals and stores it. By comparing the measurement images, the surface of the object E2 can be calculated.

FIG. 7 shows, as an example, the measurement image of a ^Lego® game module that was created using the device according to the invention.

The conversion for determining the tread depth is effected by the evaluation unit 17 shown in FIG. 1, which comprises a processor unit and is controlled by suitable program steps for evaluating the data according to the light-slit triangulation method.

Claims

claims

A method for detecting the three-dimensional surface of an object in which a light beam (12a) is emitted from a light source (11) and inclined onto the surface (16a) of the object (16) to be detected, projecting from the surface (16a ) is detected by an optical sensor (15) in order to determine the surface (16a) of the object (16) from image data generated by the optical sensor (15), characterized in that the light emitted onto the Surface (16 a) of the object (16) projected light beam

(12a) by means of a rotating prism (13) parallel to it

Beam axis is shifted so that it has the surface to be detected

(16a) of the object (16) sweeps over at a constant angle of inclination (α).

2. The method according to claim 1, characterized in that the light beam (12) is formed as a 2-dimensional illumination line which extends transversely to the beam axis, and which is moved parallel to the projected to the surface to be detected (16a) illumination line during the measurement.

3. The method according to claim 1 or 2, characterized in that as object (16) a vehicle tire is used, and from the image data, the tread depth of the vehicle tire is determined.

4. The method according to claim 2 or 3, characterized in that the object (16) is illuminated by a gap (26), wherein the illumination line extends in the longitudinal direction of the gap (26) and during the measurement, the width of the gap (26). sweeps.

5. The method according to any one of the preceding claims, characterized in that the surface to be detected (16a) relative to the optical sensor (15) is at rest, while the light beam (12a) sweeps over the surface (16a).

6. The method according to any one of the preceding claims, characterized in that the emitted light beam (12a) after passing through the prism (13) by means of an adjustable mirror device (14) is directed to the object (16).

7. The method according to any one of the preceding claims, characterized in that the emitted light beam (12a) passes through the rotating prism (13) and is moved in parallel, and the light beam (12b) reflected by the object (16), the rotating prism (13) runs through the second time, with the parallel shift caused by the first pass canceled out again.

8. The method according to any one of the preceding claims, characterized in that the object (16) transmitted light beam (12a) by means of the mirror device (14) is aligned such that it is parallel to the object (16) reflected light beam (12b) ,

9. The method according to any one of the preceding claims, characterized in that the light beam (12a) before impacting the object (16) by means of auxiliary mirrors (41, 42) is deflected so that it obliquely on the surface (16a) of the object (16 16) is incident.

An apparatus for detecting the three-dimensional surface of an object, comprising: a light source (11) emitting a light beam (12a); a mirror device (14) for inclining the emitted light beam (12a) towards a surface (16a) of an object (16) to be detected project; an optical sensor (15) which detects the light beam (12b) reflected from the surface (16a) and generates image data, an evaluation unit (17) consisting of the image data of the optical sensor

(15) the surface (16a) of the object (16) is characterized by a rotatable prism (13) which shifts the light beam (12a) projected onto the surface (16a) of the object (16) parallel to its beam axis, thus that he the surface to be detected (16a) of the object

(16) passes under a constant angle of inclination (α).

11. The device according to claim 10, characterized in that the light source (11) is designed such that the light beam (12a) is formed as a line of illumination extending transversely to the beam direction, wherein the axis of rotation (18) of the prism (13) in the level of the illumination line is located.

12. The apparatus of claim 10 or 11, characterized in that the object (16) is a vehicle tire, and the evaluation unit (17) for determining the tread depth of the vehicle tire from the image data is configured.

13. Device according to one of claims 10 to 12, characterized in that the rotatable prism (13) has an even number of surfaces (13a, 13b, 13c, 13d, 13e, 13f).

14. The device according to one of claims 10 to 13, characterized in that the rotatable prism (13) each opposite, parallel aligned surfaces (13a, 13e) through which the emitted light beam (12a) is guided.

15. Device according to one of claims 11 to 13, characterized by a wall (27) in which a gap (26) is formed, through which the object (16) is illuminated, wherein the gap (26) extends parallel to the illumination line ,

16. The apparatus according to claim 15, characterized in that the dimensions of the prism (13) are selected such that the parallel displacement of the projected to the surface to be detected (16 a) lighting line substantially corresponds to the width of the gap (26).

17. Device according to one of claims 10 to 16, characterized in that the mirror device (14) has at least one pair of mirrors with mutually inclined mirrors (14a, 14b) to direct the light beam (12a) on the object (16) while he is moved in parallel.

18. The apparatus according to claim 17, characterized in that the pair of mirrors (14a, 14b) is displaceable in the beam direction and the angle between the two mirrors (14a, 14b) is adjustable.

19. Device according to one of claims 10 to 18, characterized in that the rotatable prism (13) is arranged in the beam path such that both the emitted light beam (12a) and the object (16) reflected light beam, the prism (13). passes through, so that the two parallel displacements of the light beam (12a, 12b) cancel each other in the respective passage through the prism (13).

20. Device according to one of the preceding claims 10 to 19, characterized in that the mirror device (14) is designed such that the object (16) transmitted light beam (12a) substantially parallel to the light reflected from the object (16) (12b) runs.

21. Device according to one of the preceding claims 10 to 20, characterized in that the mirror device (14) auxiliary mirror (41, 42) which deflect the on the object (16) directed light beam (12a) such that it obliquely on the Surface (16a) of the object (16) meets.

22. Device according to one of the preceding claims 10 to 21, characterized by a housing (21) having windows (24, 25) with self-cleaning surfaces through which the emitted and / or reflected from the object light beam (12 a, 12 b) out becomes.